Wellbores are formed in subterranean formations for various purposes including, for example, extraction of oil and gas from the subterranean formation and extraction of geothennal heat from the subterranean formation. Wellbores may be formed in a subterranean formation using a drill bit such as, for example, an earth-boring rotary drill bit. Different types of earth-boring rotary drill bits are known in the art including, for example, fixed-cutter bits (which are often referred to in the art as “drag” bits), rolling-cutter bits (which are often referred to in the art as “rock” bits), diamond-impregnated bits, and hybrid bits (which may include, for example, both fixed cutters and rolling cutters). The drill bit is rotated and advanced into the subterranean formation. As the drill bit rotates, the cutters or abrasive structures thereof cut, crush, shear, and/or abrade away the formation material to form the wellbore. A diameter of the wellbore drilled by the drill bit may be defined by the cutting structures disposed at the largest outer diameter of the drill bit.
The drill bit is coupled, either directly or indirectly, to an end of what is referred to in the art as a “drill string,” which comprises a series of elongated tubular segments connected end-to-end that extends into the wellbore from the surface of the formation. Various tools and components, including the drill bit, may be coupled at the distal end of the drill string at the bottom of the wellbore being drilled. This assembly of tools and components is referred to in the art as a “bottom hole assembly” (BHA).
Wirelines can also be used in a wellbore as part of drilling operations or during post-drilling operations. A “wireline” or “slickline,” both terms used in the art, comprises a long wire or cable used to lower and raise downhole tools used in oil and gas wells for various purposes. Conductors for providing power and transmitting data may be incorporated in wirelines.
Coiled tubing, which comprises a thin-walled, highly flexible, continuous metal conduit that is transported to a well site and fed into a well bore from a reel, may be used in lieu of wireline for the same, and addition purposes.
A drill string, wireline, coiled tubing and/or a BHA may be used to deploy, or may include, a number of components in addition to the aforementioned components, including without limitation drill pipe, drill collars, stabilizers, measuring-while-drilling (MWD) equipment, logging-while-drilling (LWD) equipment, downhole communication modules, detectors, and other components. MWD/LWD and other wellbore tools may be disposed in an existing wellbore for, among other operations, completing, testing, stimulating, producing, and remediating hydrocarbon-bearing formations.
MWD/LWD tools are typically designed to determine or monitor downhole conditions or parameters. These tools may be configured to determine formation parameters, including, among other things, the resistivity, porosity, and permeability of the rock formation surrounding the wellbore drilled for recovering hydrocarbons. MWD/LWD tools may also be configured to measure the diameter of the borehole or the temperature, pressure, and humidity in the wellbore.
Because of the prolonged contact of wellbore tools with pressurized, solids-laden fluids and debris, and with the wall of the wellbore, in addition to the generally harsh conditions of a downhole location in terms of temperature and often-corrosive fluids, when drilling, completing, testing, stimulating, producing or remediating a wellbore, surfaces of drill bits, drill strings, tool strings, wirelines, MWD/LWD tools, and components thereof become damaged due to erosion, abrasion, and/or corrosion. Damage may occur on interior and/or exterior surfaces of such components. Damage may lead to premature failure of components and to additional costs associated with removal and repair or replacement of damaged components. Coatings are often provided on wellbore tools to protect the tools from the harsh environments in which they are used.